1. Field of the Invention
This invention relates to novel amine compounds useful as a basic component in resist compositions, novel resist compositions suitable for microfabrication comprising the amine compounds, and a patterning processing using the same.
While a number of efforts are currently made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. Deep-UV lithography is capable of pattern generation to dimensions of 0.2 xcexcm or less and, when a resist material having low light absorption is used, can form patterns with sidewalls that are nearly vertical to the substrate. One technology that has attracted a good deal of attention recently utilizes a high-intensity KrF excimer laser as the deep-UV light source. Resist materials with low light absorption and high sensitivity are needed to successfully apply this technology to large-volume production.
In light of this, acid-catalyzed chemically amplified positive resist materials were recently developed as disclosed in JP-B 2-27660, JP-A 63-27829, U.S. Pat. Nos. 4,491,628 and 5,310,619. Because of their excellent properties including sensitivity, resolution and dry-etching resistance, they are especially promising as resist materials for deep-UV lithography.
Chemically amplified resist materials; however, suffer from a post-exposure delay (PED) problem and a footing phenomenon. The PED problem is that in lithographic process, line patterns would have a T-top profile, that is, patterns become thick at the top if the leave-to-stand or delay time from exposure to post-exposure baking (PEB) is extended. The footing is a phenomenon that a pattern on a basic substrate, especially silicon nitride or titanium nitride substrate becomes widened in proximity to the substrate. It is believed that the T-top profile arises because the solubility of resist film is reduced in proximity to its lo surface whereas the footing arises because the solubility of resist film is reduced in proximity to the substrate. There also occurs a problem that dark reaction of eliminating acid labile groups proceeds in a PED duration from exposure to PEB, reducing the dimension of lines to be left. These problems are serious enough to prevent chemically amplified positive resist materials from practical application. Moreover, these problems not only complicate dimensional control in the lithographic process, but also adversely affect dimensional control in the processing of substrates using dry etching. In this regard, reference is made to W. Hinsberg et al., J. Photopolym. Sci. Technol., 6 (4), 535-546 (1993) and T. Kumada et al., J. Photopolym., Sci. Technol., 6 (4), 571-574 (1993). It is understood that in chemically amplified positive resist materials, air-borne basic compounds largely participate in the PED problem and basic compounds on the substrate surface largely participate in the footing phenomenon. Light exposure generates acid at the resist surface which is deactivated through reaction with air-borne basic compounds. As the leave-to-stand or delay time from exposure to PEB is extended, the amount of thus deactivated acid increases to retard decomposition of acid labile groups. An insolubilized layer is then formed at the resist surface, resulting in a T-top profile.
It is well known that the addition of basic compounds to resist materials is effective to suppress the influence of air-borne basic compounds, thereby improving PED (see U.S. Pat. No. 5,609,989, WO 98/37458, JP-A 63-149640, JP-A 5-113666, JP-A 5-232706 and JP-A 5-249683). Among such basic compounds, nitrogenous compounds are well known, typically amine and amide compounds having a boiling point of 150xc2x0 C. or higher. Illustrative examples include pyridine, polyvinyl pyridine, aniline, N-methylaniline, N,N-dimethylaniline, o-toluidine, m-toluidine, p-toluidine, 2,4-lutidine, quinoline, isoquinoline, formamide, N-methylformamide, N,N-dimethyl-formamide, acetamide, N-methylacetamide, N,N-dimethylacet-amide, 2-pyrrolidone, N-methylpyrrolidone, imidazole, xcex1-picoline, xcex2-picoline, xcex3-picoline, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 2-quinoline-carboxylic acid, 2-amino-4-nitrophenol, and triazine compounds such as 2-(p-chlorophenyl)-4,6-trichloromethyl-s-triazine. Of these, pyrrolidone, N-methylpyrrolidone, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid and 1,2-phenylenediamine are often used.
These nitrogenous compounds are weakly basic and can mitigate the T-top problem, but fail to control reaction or acid diffusion when highly reactive acid labile groups are used. The addition of weak bases allows the dark reaction during PED to proceed to unexposed areas, incurring sliming of line size and film thinning on line surface during PED. This problem may be overcome by adding strong bases. However, a higher basicity does not always bring good results. No satisfactory results are obtained when proton sponge, DBN, and DBU, which are known as a ultra-strong base and shown below, or quaternary amines such as tetramethylammonium hydroxide are added.
Proton Sponge 
DBN: 1,5-diazabicyclo[4.3.0]-5-nonene 
DBU: 1,8-diazabicyclo[5.4.0]-7-undecene 
To enhance contrast to achieve a high resolution, it is advantageous to add a base which is more effective for complementing the acid generated. While the dissociation constant of an acid or base in water is accounted for in terms of pKa, the ability of a base to complement acid in the resist film is not directly related to the pKa of the if base. This fact is discussed in Hatakeyama et al., J. of Photopolymer Sci. and Technology, Vol. 13, No. 4, pp. 519-524 (2000).
An object of the invention is to provide a novel amine compound which is effective for preventing a resist film from thinning and for expanding the focus margin while achieving an improved resolution. Another object is to provide a resist composition comprising the same and a patterning process using the composition.
The present inventor has found that amine compounds having the following general formula (1), (2), (3) or (4), that is, amine compounds having a hydrating group such as a hydroxy, ether, ester, carbonyl, carbonate group or lactone ring and a cyclic structure are most effective for preventing a resist film from thinning and also effective for enhancing the resolution and focus margin of resist.
In a first aspect, the invention provides amine compounds as defined below.
One embodiment embraces amine compounds of the following general formula (1): 
wherein R1 is a straight or branched alkylene group of 2 to 20 carbon atoms which may contain at least one carbonyl, ether, ester or sulfide group, R2 is a straight or branched alkylene group of 1 to 10 carbon atoms, R3 is a straight, branched or cyclic alkyl or alkoxy group of 1 to 20 carbon atoms which may contain a hydroxy group, ether group, carbonyl group, ester group, lactone ring or carbonate group, and R2 and R3, taken together, may form a ring with the oxygen atom.
A second embodiment embraces amine compounds of the following general formula (2): 
wherein R1 is a straight or branched alkylene group of 2 to 20 carbon atoms which may contain at least one carbonyl, ether, ester or sulfide group, R4 is a straight or branched alkylene group of 1 to 10 carbon atoms, R5 is a single bond or a straight, branched or cyclic alkylene group of 1 to 20 carbon atoms, and R6 is hydrogen or a straight, branched or cyclic alkyl or alkoxy group of 1 to 20 carbon atoms which may contain a hydroxy group, ether group, carbonyl group, ester group, lactone ring or carbonate group.
A third embodiment embraces amine compounds of the following general formula (3): 
wherein R1 is a straight or branched alkylene group of 2 to 20 carbon atoms which may contain at least one carbonyl, ether, ester or sulfide group, R7 is a straight or branched alkylene group of 1 to 10 carbon atoms, R6 is a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hydroxy group, ether group, carbonyl group, ester group, lactone ring or carbonate group, and R7 and R8, taken together, may form a ring with the COO.
A fourth embodiment embraces amine compounds of the following general formula (4): 
wherein R1 is a straight or branched alkylene group of 2 to 20 carbon atoms which may contain at least one carbonyl, ether, ester or sulfide group, R1 is a (n+1)-valent organic group of 2 to 10 carbon atoms, R10 which may be the same or different is hydrogen or a straight, branched or cyclic alkyl or alkoxy group of 1 to 20 carbon atoms which may contain a hydroxy group, ether group, carbonyl group, ester group, lactone ring or carbonate group, and n is equal to 2, 3 or 4.
In a second aspect, the invention provides a resist composition comprising at least one of amine compounds of the general formulae (1) to (4) defined above.
The resist composition is typically a positive resist composition comprising (A) the amine compound defined above, (B) an organic solvent, (C) a base resin having an acidic functional group protected with an acid labile group, which is normally alkali,insoluble or substantially alkali insoluble, but becomes alkali soluble upon elimination of the acid labile group, and (D) a photoacid generator. The positive resist composition may further comprise (E) a dissolution inhibitor.
Alternatively, the resist composition is a negative resist composition comprising (A) the amine compound defined above, (B) an organic solvent, (Cxe2x80x2) a base resin which is normally alkali-soluble, but becomes substantially alkali insoluble when crosslinked with a crosslinker, (D) a photoacid generator, and (F) the crosslinker capable of crosslinking under the action of acid.
In a third aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition defined above onto a substrate to form a coating; heat treating the coating and then exposing it to high-energy radiation having a wavelength of less than 300 nm or electron beams through a photo mask; and optionally heat treating the exposed coating and developing it with a developer.
The amine compounds of the invention have the following general formulae (1), (2), (3) and (4). 
In formulae (1) to (4), R1 is a straight or branched alkylene group of 2 to 20 carbon atoms, and preferably 2 to 18 carbon atoms, for example, ethylene, propylene, butylene, hexylene, octylene, decylene, and dodecylene. The alkylene group may contain one or more carbonyl (xe2x95x90Cxe2x95x90O), ether (xe2x80x94Oxe2x80x94), ester (xe2x80x94COOxe2x80x94) or sulfide (xe2x80x94Sxe2x80x94) groups.
Illustrative of the group of the following formula (A) included in the above formulae (1), (2), (3) and (4) are groups of the following formulae (A)-1 to (A)-12. 
In formulae (1) to (4), R2, R4 and R7 each are a straight or branched alkylene group of 1 to 10 carbon atoms, for example, methylene, ethylene, propylene, and butylene.
R3 and R6 each are hydrogen or a straight, branched or cyclic alkyl or alkoxy group of 1 to 20 carbon atoms and preferably 1 to 10 carbon atoms. Examples include hydrogen, alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl, decyl and dodecyl, and alkoxy groups having the foregoing alkyl groups. These alkyl and alkoxy groups may contain one or more hydroxy groups, ether groups, carbonyl groups, ester groups, lactone rings or carbonate groups.
R5 is a single bond or a straight, branched or cyclic alkylene group of 1 to 20 carbon atoms, and preferably 1 to 10 carbon atoms, examples of which correspond to the above-exemplified alkyl groups, with one hydrogen atom being eliminated.
R8 is a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms and preferably 1 to 16 carbon atoms, examples of which are the same as the above-exemplified alkyl groups. The alkyl group may contain one or more hydroxy groups, ether groups, carbonyl groups, ester groups, lactone rings or carbonate groups.
It is noted that R7 and R8, taken together, may form a ring. In this event, R8 is a divalent group obtained by eliminating one hydrogen atom (attached to a carbon atom) from the above-defined group.
R9 is a (n+1)-valent organic group of 2 to 10 carbon atoms, wherein n is equal to 2, 3 or 4. Then R9 is a tri-, tetra- or penta-valent organic group. Illustrative are the hydrocarbon groups given below. 
R10 which may be the same or different is hydrogen or a straight, branched or cyclic alkyl or alkoxy group of 1 to 20 carbon atoms which may contain a hydroxy group, ether group, carbonyl group, ester group, lactone ring or carbonate group. The alkyl and alkoxy groups represented by R10 are the same as the above-exemplified ones.
The group which is directly attached to the nitrogen atom in the above formulae (1), (2), (3) and (4) is of the following formulae (B1), (B2), (B3) and (B4), respectively, illustrative examples of which are groups of the following formulae (B1)-1 to (B1)-7, (B2)-1 to (B2)-13, (B3)-1 to (B3)-23, and (B4)-1 to (B4)-5. 
The amine compounds of formulae (1), (2),:(3) and (4) can be prepared by an appropriate method which is selected from several available methods depending on the structure of particular compound although the method is not limited thereto. Several exemplary methods are described below in detail.
A first method is by O-alkylation or O-acylation of an amino-alcohol compound having a cyclic amine structure. This method is especially suited for the preparation of the inventive amine compounds of formula (1), (2) and (4). In the case of O-alkylation, exemplary O-alkylating reagents include, though are not limited thereto, methyl iodide, butyl bromide, dimethyl sulfate, ethyl iodide, diethyl sulfate, methoxymethyl chloride, (2-methoxyethoxy)methyl chloride, methyl chloroacetate, and chloroacetone. In the case of O-acylation, exemplary O-acylating reagents include, though are not limited thereto, formic acid, mixed formic acid/acetic acid anhydride, acetic anhydride, acetic chloride, propionic anhydride, propionic chloride, butyric chloride, isobutyric chloride, valeric chloride, pivalic chloride, methoxyacetic chloride, acetoxyacetic chloride, di-t-butyl pyrocarboxylate, phenyl acetate, p-nitrophenyl acetate, and 2,4,6-trichlorophenyl acetate. An appropriate amount of the O-alkylating or O-acylating reagent used is 0.5 to 5.0 mol and especially 1.0 to 2.5 mol per mol of hydroxyl group in the amino-alcohol compound. Reaction is carried out in the presence or absence of solvent. The solvents which can be used herein include hydrocarbon solvents such as hexane, heptane, benzene, toluene, and xylene, ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane and diglyme, chlorinated solvents such as methylene chloride, chloroform and 1,2-dichloroethylene, aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone, carboxylic acids such as formic acid and acetic acid, esters such as ethyl acetate and butyl acetate, ketones such as acetone and 2-butanone, nitriles such as acetonitrile, and amines such as pyridine and triethylamine. Any appropriate one or mixture may be selected from these solvents depending on the reaction conditions. A basic compound may be added to promote the reaction. Illustrative, non-limiting examples of useful basic compounds include salts of alkali or alkaline earth metals such as sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, sodium hydride, calcium hydride, potassium t-butoxide and lithium t-butoxide; organometallic compounds such as n-butyl lithium, lithium diisopropylamide, lithium hexamethyl-disilazide and bromomagnesium diisopropylamide; and organic amines such as pyridine, triethylamine, diisopropylethyl-amine, N,N-dimethylaniline and 4-dimethylaminopyridine. The basic compounds may be used alone or in admixture of any. An appropriate amount of the basic compound used is 0.8 to 10 mol and especially 0.9 to 3.0 mol per mol of the O-alkylating or O-acylating reagent. In the case of O-alkylation, a catalyst may be added to accelerate the reaction, for example, sodium iodide or tetrabutylammonium iodide. The reaction temperature may be selected in the range from xe2x88x9270xc2x0 C. to the reflux temperature of the solvent and preferably in the range of 0xc2x0 C. to 50xc2x0 C. From the yield standpoint, the reaction is desirably continued to completion while monitoring the reaction by gas chromatography (GC) or thin layer chromatography (TLC), although the reaction time is usually about 0.2 to about 20 hours. From the reaction mixture, the end amine compound is obtained by a conventional aqueous work-up step. If necessary, the end amine compound is purified by any conventional technique such as distillation, chromatography or recrystallization.
As a second method, conversion like the O-acylation reaction noted in the first method is carried out by transesterification reaction between an amino-alcohol compound having a cyclic amine structure and a carboxylate in the presence of a catalyst.
This method starts with an amino-alcohol compound and carries out transesterification reaction with a carboxylate (R1CO2R2) in the presence of a catalyst to give the end compound. The reaction is carried out in the presence or absence of solvent. It is desirable for improving the yield of the end compound and reducing the reaction time that the reaction be carried out while removing the alcohol (R2OH) which is newly formed by the reaction. Illustrative, non-limiting examples of the carboxylate used herein include methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, methyl butyrate, methyl valerate, methyl pivalate, methyl cyclohexanecarboxylate, methyl methoxyacetate, methyl ethoxyacetate, methyl 2-methoxyethoxyacetate and methyl 2-(2-methoxyethoxy)ethoxy-acetate. An appropriate amount of the carboxylate used is 0.5 to 5.0 mol and especially 1.0 to 2.0 mol per mol of the starting amino-alcohol compound. Illustrative, non-limiting examples of the transesterification catalyst include organic amines such as triethylamine, 1,8-diazabicyclo[5.4.0]-7-undecene and 4-dimethylaminopyridine; inorganic bases such as sodium hydroxide, potassium carbonate and sodium carbonate; metal alkoxides such as sodium methoxide, potassium t-butoxide, magnesium ethoxide and titanium(IV) methoxide; salts such as iron(III) sulfate and calcium chloride: and inorganic or organic acids such as hydrogen chloride, sulfuric acid and p-toluenesulfonic acid. An appropriate amount of the transesterification catalyst used is 0.001 to 5.0 mol and especially 0.001 to 0.1 mol per mol of the starting amino-alcohol compound. Exemplary solvents include ethers such as tetrahydrofuran, di-n-butyl ether and 1,4-dioxane, hydrocarbons such as n-hexane, n-heptane, benzene, toluene, xylene and cumene, and chlorinated solvents such as chloroform and dichloroethylene, which may be used alone or in admixture of any. The reaction temperature varies with reaction conditions and preferably ranges from 50xc2x0 C. to 200xc2x0 C. Most preferably, reaction is carried out at a temperature near the boiling point of the reaction solvent while distilling off the alcohol (R2OH) resulting from reaction. From the yield standpoint, the reaction is desirably continued to completion while monitoring the reaction by gas chromatography (GC) or thin layer chromatography (TLC), although the reaction time is usually about 1 to about 20 hours. From the reaction mixture, the end amine compound is obtained by a conventional aqueous work-up step. If necessary, the end amine compound is purified by any conventional technique such as distillation, chromatography or recrystallization. Alternatively, the end compound can be collected by directly distilling the reaction mixture.
A third method is synthesis from a cyclic secondary amine compound and an xcex1,xcex2-unsaturated ester compound utilizing Michael addition reaction on amine. This method is especially suited for the preparation of the inventive amine compounds of formula (3).
The xcex1,xcex2-unsaturated ester compounds include acrylates and methacrylates.
An appropriate amount of the xcex1,xcex2-unsaturated ester compound used is 0.5 to 5.0 mol and especially 0.8 to 1.5 mol per mol of the cyclic secondary amine compound. The reaction is carried out in the presence or absence of solvent. Illustrative examples of the solvent include alcohols such as methanol, ethanol, isopropyl alcohol, t-butyl alcohol and ethylene glycol; hydrocarbon solvents such as hexane, heptane, benzene, toluene, and xylene; ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane and diglyme; chlorinated solvents such as methylene chloride, chloroform and 1,2-dichloroethylene; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacet-amide, dimethyl sulfoxide and N-methylpyrrolidone; carboxylic acids such as formic acid and acetic acid; esters such as ethyl acetate and butyl acetate; ketones such as acetone and 2-butanone; nitriles such as acetonitrile; amines such as pyridine and triethylamine; and water. Any appropriate one or mixture may be selected from these solvents depending on the reaction conditions. The reaction temperature is selected in the range from 0xc2x0 C. to the reflux temperature of the solvent, depending on the desired reaction rate. A catalyst may be added to the reaction system for accelerating the reaction rate. Exemplary catalysts include inorganic acids or salts thereof, such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids or salts thereof, such as p-toluenesulfonic acid, formic acid, acetic acid, oxalic acid and trifluoroacetic acid. Also, a polymerization inhibitor such as hydroquinone, p-methoxyphenol, benzoquinone or phenylenediamine may be added to preclude the xcex1,xcex2-unsaturated ester compound from polymerization. From the yield standpoint, the reaction is desirably continued to completion while monitoring the reaction by gas chromatography (GC) or thin layer chromatography (TLC), although the reaction time is usually about 2 to about 200 hours. The end amine compound is obtained from the reaction mixture directly by vacuum concentration or by a conventional aqueous work-up step and subsequent vacuum concentration. If necessary, the end amine compound thus obtained is purified by any conventional technique such as distillation, chromatography or recrystallization.
A fourth method is synthesis from a cyclic secondary amine compound and a halocarboxylic ester compound utilizing N-alkylation reaction on amine. This method is especially suited for the preparation of the inventive amine compounds of formula (3).
Illustrative, non-limiting examples of the halocarboxylic ester compound include chloroacetic esters, bromoacetic esters, 2-chloropropionic esters, 4-bromobutyric esters and 5-bromovaleric esters. An appropriate amount of the halocarboxylic ester compound used is 0.3 to 10 mol and especially 0.5 to 2.4 mol per mol of the cyclic secondary CD amine compound.
The reaction can be promoted by adding a basic compound. Illustrative, non-limiting examples-of useful basic compounds include amines such as pyridine, CD triethylamine, diisopropylethyl, N,N-dimethylaniline, to 4-dimethylaminopyridine and 1,8-diazabicyclo[5.4.0]-7-undecene; and inorganic bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium carbonate, sodium carbonate and sodium hydrogen carbonate. The basic compounds may be used alone or in admixture of any. An appropriate amount of the basic compound used is 0.1 to 10 mol and especially 0.8 to 2.0 mol per mol of the halocarboxylic ester compound. A catalyst may also be added to accelerate the reaction, for example, sodium iodide or tetrabutylammonium iodide. An appropriate amount of the catalyst used is 0.001 to 0.5 mol and especially 0.005 to 0.1 mol per mol of the halocarboxylic ester compound. The reaction is carried out in the presence or absence of solvent. Illustrative examples of the solvent include alcohols such as methanol, ethanol, isopropyl alcohol, t-butyl alcohol and ethylene glycol; hydrocarbon solvents such as hexane, heptane, benzene, toluene, and xylene; ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane and diglyme; chlorinated solvents such as methylene chloride, chloroform and 1,2-dichloroethylene; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacet-amide, dimethyl sulfoxide and N-methylpyrrolidone; carboxylic acids such as formic acid and acetic acid; esters such as ethyl acetate and butyl acetate; ketones such as acetone and 2-butanone; nitriles such as acetonitrile; amines such as pyridine and triethylamine; and water. Any appropriate one or mixture may be selected from these solvents depending on the reaction conditions. The reaction temperature is selected in the range from 0C to the reflux temperature of the solvent, depending on the desired (3 reaction rate. From the yield standpoint, the reaction is desirably continued to completion while monitoring the reaction by gas chromatography (GC) or thin layer chromatography (TLC), although the reaction time is usually about 2 to about 200 hours. The end amine compound is obtained from the reaction mixture by filtration or a conventional aqueous work-up step and subsequent vacuum concentration. If necessary, the end amine compound thus obtained is purified by any conventional technique such as distillation, chromatography or recrystallization.
The resist compositions of the invention contain one or more of the basic compounds of formulae (1), (2), (3) and (4). The amount of the amine compound blended is preferably 0.001 to 2 parts and especially 0.01 to 1 part by weight per 100 parts by weight of the entire base resin to be described later. Less than 0.001 part of the amine compound may fail to achieve the desired effects whereas more than 2 parts may result in a lower sensitivity.
The resist compositions containing the inventive amine compound may be either positive or negative working although they are preferably of the chemical amplification type.
One preferred embodiment of the invention is directed to a positive resist composition comprising
(A) the amine compound defined above,
(B) an organic solvent,
(C) a base resin having an acidic functional group protected with an acid labile group, which is normally alkali insoluble or substantially alkali insoluble, but becomes alkali-soluble upon elimination of the acid labile group,
(D) a photoacid generator, and optionally,
(E) a dissolution inhibitor.
Another preferred embodiment of the invention is directed to a negative resist composition comprising
(A) the amine compound defined above,
(B) an organic solvent,
(Cxe2x80x2) a base resin which is normally alkali-soluble, but becomes substantially alkali insoluble when crosslinked with a crosslinker,
(D) a photoacid generator, and
(F) the crosslinker capable of crosslinking under the action of acid.
Component (B) in the resist composition of the invention is an organic solvent, which may be any organic solvent in which the photoacid generator, base resin, dissolution inhibitor and other components are soluble. Usually 100 to 5,000 parts, and especially 200 to 3,000 parts by weight of the solvent is used per 100 parts by weight of the base resin. Illustrative, non-limiting, examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-amylketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; and esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate. These solvents may be used alone or in admixture of two or more. Of the above organic solvents, diethylene glycol dimethyl ether, 1-ethoxy-2-propanol and ethyl lactate in which the photoacid generator is most soluble, propylene glycol monomethyl ether acetate which is a safe solvent, and mixtures thereof are preferred.
Component (C) or (Cxe2x80x2) is a base resin. For resist compositions adapted for a KrF excimer laser, suitable base resins include polyhydroxystyrene (PHS) and copolymers of PHS with styrene, (meth)acrylates or maleimide-N-carboxylates. For resist compositions adapted for an ArF excimer laser, suitable base resins include (meth)acrylate polymers, alternating copolymers of norbornene and maleic anhydride, alternating copolymers of tetracyclododecene and maleic anhydride, norbornene polymers, and metathesis polymers by ring-opening polymerization. For resist compositions adapted for an F2 excimer laser, suitable base resins include fluorinated ones of the polymers listed for the KrF and ArF applications. These polymers are merely illustrative, and the base resin used herein is not limited thereto. For positive resist compositions, it is a common practice to reduce the dissolution rate of unexposed areas by partially substituting acid labile groups for phenolic hydroxyl groups or carboxyl groups or hydroxyl groups on fluorinated alkyl alcohols.
In the base resin, the acid labile group is selected from a variety of such groups, and preferably from among groups of the following general formulae (8) and (9), tertiary alkyl groups with 4 to 40 carbon atoms of the following general formula (10), trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms. 
In formula (8), R11 is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group whose alkyl groups each have 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms or a group of formula (10). Exemplary tertiary alkyl groups are tert-butyl, tert-amyl, 1,1-diethylpropyl, 1-ethylcyclo-pentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclo-hexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. Letter xe2x80x9calxe2x80x9d is an integer of 0 to 6.
In formula (9), R12 and R13 are independently hydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl and n-octyl. R14 is a monovalent hydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may have a hetero atom such as oxygen atom, for example, straight, branched or cyclic alkyl groups, and such groups in which some hydrogen atoms are replaced by hydroxyl, alkoxy, oxo, amino or alkylamino groups. Illustrative examples of the substituted alkyl groups are given below. 
A pair of R12 and R13, a pair of R12 and R14, or a pair of R13 and R14, taken together, may form a ring. Each of R12, R13 and R14 is a straight or branched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, when they form a ring.
Illustrative examples of the acid labile groups of formula (8) include tert-butoxycarbonyl, tert-butoxy-carbonylmethyl, tert-amyloxycarbonyl, tert-amyloxycarbonyl-methyl, 1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxy-carbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclo-pentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl, 1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxy-carbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl.
Substituent groups of the following formulae (8)-1 through (8)-9 are also included. 
Herein, R18 which is identical or different is a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 20 carbon atoms. R19 is hydrogen or a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms. R20 which is identical or different is a straight, branched or cyclic alkyl group of 2 to 10 carbon atoms or an aryl group of 6 to 20 carbon atoms.
Of the acid labile groups of formula (9), straight or branched groups are exemplified by the following formulae (9)-1 through (9)-23. 
Of the acid labile groups of formula (9), illustrative examples of the cyclic groups include tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl and 2-methyltetrahydropyran-2-yl.
The base resin may be crosslinked within the molecule or between molecules with acid labile groups of the following general formula (9a) or (9b). 
Herein R21 and R22 each are hydrogen or a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, or R21 and R22, taken together, may form a ring, and R21 and R22 are straight or branched alkylene groups of 1 to 8 carbon atoms when they form a ring; R23 is a straight, branched or cyclic alkylene group of 1 to 10 carbon atoms; xe2x80x9cbxe2x80x9d and xe2x80x9cdxe2x80x9d are 0 or integers of 1 to 10, and preferably 0 or an integer of 1 to 5; xe2x80x9ccxe2x80x9d is an integer of 1 to 7; xe2x80x9cAxe2x80x9d is a (c+1)-valent aliphatic or alicyclic saturated hydrocarbon group, aromatic hydrocarbon group or heterocyclic group having 1 to 50 carbon atoms, which may be separated by a hetero atom or in which some of the hydrogen atoms attached to carbon atoms may be substituted with hydroxyl, carboxyl, carbonyl or fluorine; and B is xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NHCOxe2x80x94Oxe2x80x94 or xe2x80x94NHCONHxe2x80x94.
Preferably, xe2x80x9cAxe2x80x9d is selected from di- to tetra-valent straight, branched or cyclic alkylene groups of 1 to 20 carbon atoms, alkyltriyl groups, alkyltetrayl groups and arylene groups of 6 to 30 carbon atoms, which may be separated by a hetero atom and in which some of the hydrogen atoms attached to carbon atoms may be substituted with hydroxyl, carboxyl or acyl groups or halogen atoms. The letter xe2x80x9ccxe2x80x9d is preferably an integer of 1 to 3.
The crosslinking acetal groups of formulae (9a) and (9b) are exemplified by the following formulae (9)-24 through (9)-35. 
Next, in formula (10), R15, R16 and R17 each are a monovalent hydrocarbon group, typically a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, which may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine. A pair of R15 and R16, R15 and R17, and R16 and R17, taken together, may form a ring of 3 to 20 carbon atoms with the carbon atom.
Examples of the tertiary alkyl group represented by formula (10) include tert-butyl, triethylcarbyl, 1-ethyl-norbornyl, 1-methylcyclohexyl, 1-ethylcyclopentyl, 2-(2-methyl)adamantyl, 2-(2-ethyl)adamantyl, and tert-amyl.
Other illustrative examples of the tertiary alkyl group are given below as formulae (10)-1 through (10)-18. 
In formulae (10)-1 through (10)-18, R24 which may be identical or different is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or an aryl group of 6 to 20 carbon atoms, typically phenyl. R25 and R27 each are hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms. R26 is an aryl group of 6 to 20 carbon atoms, typically phenyl.
Further, the polymer may be crosslinked within the molecule or between molecules by incorporating R28 which is a divalent or more valent alkylene or arylene group as shown by the following formulae (10)-19 and (10)-20. 
In formulae (10)-19 and (10)-20, R24 is as defined above; R28 is a straight, branched or cyclic alkylene group of 1 to 20 carbon atoms or an arylene group such as. phenylene, which may contain a hetero atom such as an oxygen, sulfur or nitrogen atom; and b1 is an integer of 1 to 3.
Further, R15, R16 and R17 in formula (10) may have a hetero atom such as oxygen, nitrogen or sulfur. Such groups are exemplified below by formulae (11)-1 through (11)-9.
In formulae (8), (9) and (10), R11, R14 and R17 may also stand for substituted or unsubstituted aryl groups such as phenyl, p-methylphenyl, p-ethylphenyl and alkoxy-substituted phenyl such as p-methoxyphenyl, and aralkyl groups such as benzyl and phenethyl, or alkyl groups of formulae (11)-1 to (11)-5 and oxoalkyl groups of formulae (11)-6 to (11)-9. 
Of the acid labile groups, the trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms include trimethylsilyl, triethylsilyl, and tert-butyldimethylsilyl.
The oxoalkyl groups of 4 to 20 carbon atoms include 3-oxocyclohexyl and groups of the following formulae. 
It is noted that the base resin (C) preferably has a weight average molecular weight (Mw) of about 5,000 to about 100,000. A polymer with a Mw of less than 5,000 may have poor film formability and resolution whereas a polymer with a Mw of more than 100,000 may have poor resolution.
Suitable examples of the photoacid generator (D) include onium salts of general formula (12) below, diazomethane derivatives of formula (13), glyoxime derivatives of formula (14), xcex2-ketosulfone derivatives, disulfone derivatives, nitrobenzylsulfonate derivatives, sulfonic acid ester derivatives, and imidoyl sulfonate derivatives.
xe2x80x83(R30)bM+Kxe2x88x92xe2x80x83xe2x80x83(12)
In the formula, R30 is a straight, branched or cyclic alkyl of 1 to 12 carbon atoms, an aryl of 6 to 12 carbon atoms, or an aralkyl of 7 to 12 carbon atoms; M+ is iodonium or sulfonium: Kxe2x88x92 is a non-nucleophilic counter-ion; and the letter b is 2 or 3.
Illustrative examples of alkyl groups represented by R30 include methyl, ethyl, propyl, butyl, cyclohexyl, 2-oxocyclohexyl, norbornyl, and adamantyl. Exemplary aryl groups include phenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, and m-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl, 4-butyl-phenyl, and dimethylphenyl. Exemplary aralkyl groups include benzyl and phenethyl. Examples of the non-nucleophilic counter-ion represented by Kxe2x88x92 include halide ions such as chloride and bromide; fluoroalkylsulfonate ions such as triflate, 2,2,2-trifluoroethanesulfonate, and nonafluorobutanesulfonate; arylsulfonate ions such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and 2,3,4,5,6-pentafluorobenzenesulfonate; and alkylsulfonate ions such as mesylate and butanesulfonate. 
In the formula, R31 and R32 are straight, branched or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, aryl or halogenated aryl groups of 6 to 12 carbon atoms, or aralkyl groups of 7 to 12 carbon atoms.
Illustrative examples of alkyl groups represented by R31 and R32 include methyl, ethyl, propyl, butyl, amyl, cyclopentyl, cyclohexyl, norbornyl, and adamantyl. Exemplary halogenated alkyl groups include trifluoromethyl, 2,2,2-trifluoroethyl, 2,2,2-trichloroethyl, and nonafluoro-butyl. Exemplary aryl groups include phenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl, o-methoxy-phenyl, ethoxyphenyl, p-tert-butoxyphenyl, and m-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl, 4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groups include fluorobenzene, chlorobenzene, and 2,3,4,5,6-pentafluorobenzene. Exemplary aralkyl groups include benzyl and phenethyl. 
In the formula, R33, R34, and R35 are straight, branched kD or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, aryl or halogenated aryl groups of 6 to 12 carbon atoms, or aralkyl groups of 7 to 12 carbon atoms. R34 and R35 may together form a cyclic structure with the proviso that if they form a cyclic structure, each is a straight or branched alkylene group of 1 to 6 carbon atoms.
The alkyl, halogenated alkyl, aryl, halogenated aryl, and aralkyl groups represented by R33, R34, and R35 are exemplified by the same groups as mentioned above for R31 and R32. Examples of alkylene groups represented by R34 and R35 include methylene, ethylene, propylene, butylene, and hexylene.
Illustrative examples of the photoacid generator include:
onium salts such as diphenyliodonium trifluoromethane-sulfonate, (p-tert-butoxyphenyl)phenyliodonium trifluoro-methanesulfonate, diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethane-sulfonate, tris(p-tert-butoxyphenyl)sulfonium trifluoro-methanesulfonate, triphenylsulfonium p-toluenesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate, bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate, tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate, triphenylsulfonium nonafluorobutanesulfonate, triphenyl-sulfonium butanesulfonate, trimethylsulfonium trifluoro-methanesulfonate, trimethylsulfonium p-toluenesulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethane-sulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate, dimethylphenylsulfonium trifluoromethane-sulfonate, dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfonium trifluoromethanesulfonate, and dicyclohexylphenylsulfonium p-toluenesulfonate;
diazomethane derivatives such as bis(benzenesulfonyl)-diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(xylenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)-diazomethane, bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazo-methane, bis(sec-butylsulfonyl)diazomethane, bis(n-propyl-sulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane, bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)-diazomethane, bis(isoamylsulfonyl)diazomethane, bis(secamylsulfonyl)diazomethane, bis(tert-amylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and 1-tert-amylsulfonyl-1-(tert-butyl-sulfonyl)diazomethane;
glyoxime derivatives such as bis-O-(p-toluene-sulfonyl)-xcex1-dimethylglyoxime, bis-O-(p-toluenesulfonyl)-xcex1-diphenylglyoxime, bis-O-(p-toluenesulfonyl)-xcex1-dicyclohexyl-glyoxime, bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime, bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime, bis-O-(n-butanesulfonyl)-xcex1-dimethylglyoxime, bis-O-(n-butanesulfonyl)-xcex1-diphenylglyoxime, bis-O-(n-butanesulfonyl)-xcex1-dicyclohexylglyoxime, bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime, bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime, bis-O-(methanesulfonyl)-xcex1-dimethylglyoxime, bis-O-(trifluoromethanesulfonyl)-xcex1-dimethylglyoxime, bis-O-(1,1,1-trifluoroethanesulfonyl)-xcex1-dimethylglyoxime, bis-O-(tert-butanesulfonyl)-xcex1-dimethyl-glyoxime, bis-O-(perfluorooctanesulfonyl)-xcex1-dimethylglyoxime, bis-O-(cyclohexanesulfonyl)-xcex1-dimethylglyoxime, bis-O-(benzenesulfonyl)-xcex1-dimethylglyoxime, bis-O-(p-fluoro-benzenesulfonyl)-xcex1-dimethylglyoxime, bis-O-(p-tert-butyl-benzenesulfonyl)-xcex1-dimethylglyoxime, bis-O-(xylenesulfonyl)-xcex1-dimethylglyoxime, and bis-O-(camphorsulfonyl)-xcex1-dimethyl-glyoxime;
xcex2-ketosulfone derivatives such as 2-cyclohexyl-carbonyl-2-(p-toluenesulfonyl)propane and 2-isopropyl-carbonyl-2-(p-toluenesulfonyl)propane;
disulfone derivatives such as diphenyl disulfone and dicyclohexyl disulfone;
nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzyl p-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;
sulfonic acid ester derivatives such as 1,2,3-tris(methanesulfonyloxy)benzene, 1.2,3-tris(trifluoro-methanesulfonyloxy)benzene, and 1,2,3-tris(p-toluene-sulfonyloxy)benzene; and
imidoyl sulfonate derivatives such as phthalimidoyl triflate, phthalimidoyl tosylate, 5-norbornene-2,3-dicarboxyimidoyl triflate, 5-norbornene-2,3-dicarboxyimidoyl tosylate, and 5-norbornene-2,3-dicarboxyimidoyl n-butyl-sulfonate.
Preferred among these photoacid generators are onium salts such as triphenylsulfonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethane-sulfonate, tris(p-tert-butoxyphenyl)sulfonium trifluoro-methanesulfonate, triphenylsulfonium p-toluenesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate, and tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate; diazomethane derivatives such as bis(benzenesulfonyl)diazo-methane, bis(p-toluenesulfonyl)diazomethane, bis(cyclohexyl sulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane, bis(sec-butyl-sulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane, and bis(tert-butyl-sulfonyl)diazomethane; and glyoxime derivatives such as bis-O-(p-toluenesulfonyl)-xcex1-dimethylglyoxime and bis-O-(n-butanesulfonyl)-xcex1-dimethylglyoxime; and naphthoquinone-diazidosulfonate derivatives. These photoacid generators may be used singly or in combinations of two or more thereof. Onium salts are effective for improving rectangularity, while diazomethane derivatives and glyoxime derivatives are effective for reducing standing waves. The combination of an onium salt with a diazomethane or a glyoxime derivative allows for fine adjustment of the profile.
The photoacid generator is preferably added in an amount of about 0.2 to 50 parts by weight, and especially about 0.5 to 40 parts by weight, per 100 parts by weight of the entire base resin. At less than 0.2 part, the amount of acid generated during exposure may be too small, resulting in poor sensitivity and resolution. The addition of more than 50parts may lower the transmittance of the resist and result in a poor resolution.
The dissolution inhibitor (E) is a compound with a molecular weight of up to 3,000 which changes its solubility in an alkaline developer under the action of an acid. Typically, a compound obtained by partially or entirely substituting acid labile substituents on a phenol or carboxylic acid derivative having a molecular weight of up to 2,500 is added as the dissolution inhibitor.
Examples of the phenol or carboxylic acid derivative having a molecular weight of up to 2,500 include bisphenol A, bisphenol H, bisphenol S, 4,4-bis(4xe2x80x2-hydroxyphenyl)valeric acid, tris(4-hydroxyphenyl)methane, 1,1,1-tris(4xe2x80x2-hydroxy-phenyl)ethane, 1,1,2-tris(4xe2x80x2-hydroxyphenyl)ethane, phenolphthalein, and thimolphthalein. The acid labile substituents are the same as exemplified for R4.
Illustrative, non-limiting, examples of the dissolution inhibitors which are useful herein include
bis(4-(2xe2x80x2-tetrahydropyranyloxy)phenyl)methane,
bis(4-(2xe2x80x2-tetrahydrofuranyloxy)phenyl)methane,
bis(4-tert-butoxyphenyl)methane,
bis(4-tert-butoxycarbonyloxyphenyl)methane,
bis(4-tert-butoxycarbonylmethyloxyphenyl)methane,
bis(4-(1xe2x80x2-ethoxyethoxy)phenyl)methane,
bis(4-(1xe2x80x2-ethoxypropyloxy)phenyl)methane,
2,2-bis(4xe2x80x2-(2xe2x80x3-tetrahydropyranyloxy))propane,
2,2-bis(4xe2x80x2-(2xe2x80x3-tetrahydrofuranyloxy)phenyl)propane,
2,2-bis(4xe2x80x2-tert-butoxyphenyl)propane,
2,2-bis(4xe2x80x2-tert-butoxycarbonyloxyphenyl)propane,
2,2-bis(4-tert-butoxycarbonylmethyloxyphenyl)propane,
2,2-bis(4xe2x80x2-(1xe2x80x3-ethoxyethoxy)phenyl)propane,
2,2-bis(4xe2x80x2-(1xe2x80x3-ethoxypropyloxy)phenyl)propane,
tert-butyl 4,4-bis(4xe2x80x2-(2xe2x80x3-tetrahydropyranyloxy)phenyl)-valerate,
tert-butyl 4,4-bis(4xe2x80x2-(2xe2x80x3-tetrahydrofuranyloxy)phenyl)-valerate,
tert-butyl 4,4-bis(4xe2x80x2-tert-butoxyphenyl)valerate,
tert-butyl 4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate,
tert-butyl 4,4-bis(4xe2x80x2-tert-butoxycarbonylmethyloxyphenyl)-valerate,
tert-butyl 4,4-bis(4xe2x80x2-(1xe2x80x3-ethoxyethoxy)phenyl)valerate,
tert-butyl 4,4-bis(4xe2x80x2-(1xe2x80x3-ethoxypropyloxy)phenyl)valerate,
tris(4-(2xe2x80x2-tetrahydropyranyloxy)phenyl)methane,
tris(4-(2xe2x80x2-tetrahydrofuranyloxy)phenyl)methane.
tris(4-tert-butoxyphenyl)methane,
tris(4-tert-butoxycarbonyloxyphenyl)methane,
tris(4-tert-butoxycarbonyloxymethylphenyl)methane,
tris(4-(1xe2x80x2-ethoxyethoxy)phenyl)methane,
tris(4-(1xe2x80x2-ethoxypropyloxy)phenyl)methane,
1,1,2-tris(4xe2x80x2-(2xe2x80x3-tetrahydropyranyloxy)phenyl)ethane.
1,1,2-tris(4xe2x80x2-(2xe2x80x3-tetrahydrofuranyloxy)phenyl)ethane,
1,1,2-tris(4xe2x80x2-tert-butoxyphenyl)ethane,
1,1,2-tris(4xe2x80x2-tert-butoxycarbonyloxyphenyl)ethane,
1,1,2-tris(4xe2x80x2-tert-butoxycarbonylmethyloxyphenyl)ethane,
1,1,2-tris(4xe2x80x2-(1xe2x80x2-ethoxyethoxy)phenyl)ethane, and
1,1,2-tris(4xe2x80x2-(1xe2x80x2-ethoxypropyloxy)phenyl)ethane.
An appropriate amount of the dissolution inhibitor is up to 20 parts, and especially up to 15 parts by weight per 100 parts by weight of the solids in the resist composition. With more than 20 parts of the dissolution inhibitor, the resist composition becomes less heat resistant because of an increased content of monomer components.
Formulated in the negative resist composition is an crosslinker (F) which forms a crosslinked structure under the action of acid. Typical crosslinkers are compounds having at least two hydroxymethyl, alkoxymethyl, epoxy or vinyl ether groups within a molecule. Substituted glycoluril derivatives, urea derivatives, and hexa(methoxy-methyl)melamine compounds are suitable as the crosslinker. Examples include: N,N,Nxe2x80x2,Nxe2x80x2-tetramethoxymethylurea, hexa-methoxymethylmelamine, tetraalkoxymethyl-substituted glycoluril compounds such as tetrahydroxymethyl-substituted glycoluril and tetramethoxymethylglycoluril, and condensates of phenolic compounds such as substituted or unsubstituted bis(hydroxymethylphenol) compounds and bisphenol A with epichlorohydrin. Especially preferred crosslinkers are 1,3,5,7-tetraalkoxymethylglycolurils such as 1,3,5,7-tetra-methoxymethylglycoluril, 1,3,5,7-tetrahydroxymethyl-glycoluril, 2,6-dihydroxymethyl-p-cresol, 2,6-dihydroxy-methylphenol, 2,2xe2x80x2,6,6xe2x80x2-tetrahydroxymethyl-bisphenol A, 1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,Nxe2x80x2,Nxe2x80x2-tetramethoxy-methylurea, and hexamethoxymethylmelamine. In the resist composition, an appropriate amount of the crosslinker is, though not limited thereto, about 1 to 25 parts, and especially about 5 to 20 parts by weight per 100 parts by weight of the solids in the composition. The crosslinkers may be used alone or in admixture of two or more.
In addition to the inventive basic compound, one or more of commonly used bases may be employed in the inventive resist composition. Examples of suitable conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, carboxyl group-bearing nitrogenous compounds, sulfonyl group-bearing nitrogenous compounds, hydroxyl group-bearing nitrogenous compounds, hydroxyphenyl group-bearing nitrogenous compounds, alcoholic nitrogenous compounds, amide derivatives, and imide derivatives.
Examples of suitable primary aliphatic amines include ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, iso-butylamine, sec-butylamine, tert-butylamine, pentylamine, tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, cetylamine, methylenediamine, ethylenediamine, and tetraethylenepentamine. Examples of suitable secondary aliphatic amines include dimethylamine, diethylamine, di-n-propylamine, di-iso-propylamine, di-n-butylamine, di-iso-butylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine, dicyclohexylamlne, diheptylamine, dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine, N,N-dimethyl-methylenediamine, N,N-dimethylethylenediamine, and N,N-dimethyltetraethylenepentamine. Examples of suitable tertiary aliphatic amines include trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tripentylamine, tricyclopentylamlne, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylmethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetra-methylethylenediamine, and N,N,Nxe2x80x2,Nxe2x80x2-tetramethyltetraethylenepentamine.
Examples of suitable mixed amines include dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine, and benzyldimethylamlne. Examples of suitable aromatic and heterocyclic amines include aniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, ethylaniline, propylaniline, trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazole derivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g., thiazole and isothiazole), imidazole derivatives (e.g., imidazole, 4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives, pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives, imidazolidine derivatives, pyrldlne derivatives (e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine, butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine, triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine, benzylpyrldine, methoxypyridine, butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyrldine, 2-(1-ethylpropyl)-pyrldine, aminopyridine, and dimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives, piperidine derivatives, piperazine derivatives, morpholine derivatives, indole derivatives, isoindole derivatives, 1H-indazole derivatives, indoline derivatives, quinoline derivatives (e.g., quinoline and 3-quinoline-carbonitrile), isoquinoline derivatives, cinnoline derivatives, quinazoline derivatives, quinoxaline derivatives, phthalazine derivatives, purine derivatives, pteridine derivatives, carbazole derivatives, phenanthridine derivatives, acridine derivatives, phenazine derivatives, 1,10-phenanthroline derivatives, adenine derivatives, adenosine derivatives, guanine derivatives, guanosine derivatives, uracil derivatives, and uridine derivatives.
Examples of suitable carboxyl group-bearing nitrogenous compounds include aminobenzoic acid, indolecarboxylic acid, and amino acid derivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine, methionine, phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples of suitable sulfonyl group-bearing nitrogenous compounds include 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples of suitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenyl group-bearing nitrogenous compounds, and alcoholic nitrogenous compounds include 2-hydroxypyridine, aminocresol, 2,4-guinolinediol. 3-indolemethanol hydrate, monoethanolamine, diethanolamine, triethanolamine. N-ethyldiethanolamine. N,N-diethylethanolamine, trilsopropanolamine, 2,2xe2x80x2-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]-piperazine, piperidine ethanol, 1-(2-hydroxyethyl)-pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol, N-(2-hydroxy-ethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide. Examples of suitable amide derivatives include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methyl-acetamide, N,N-dimethylacetamide, propionamide, and benzamide. Suitable imide derivatives include phthalimide, succinimide, and maleimide.
In addition, basic compounds of the following general formulas (B)-100 and (B)-101 may also be included. 
In the formulas, R41, R42, R43 R47 and R48 are independently straight, branched or cyclic alkylenes of 1 to 20 carbon atoms; R44, R45, R46, R49 and R50 are hydrogen, alkyls of 1 to 20 carbon atoms, or amino; R44 and R45, R45 and R46, R44 and R46, R44 with R45 and R46, and R49 and R50 may bond together to form rings; and S, T and U are each integers from 0 to 20, with the proviso that hydrogen is excluded from R44, R45, R46, R49 and R50 when S, T and U are equal to 0.
The alkylene groups represented by R41, R42, R43, R47 and R48 preferably have 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and most preferably 1 to 8 carbon atoms. Examples include methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, n-pentylene, isopentylene, hexylene, nonylene, decylene, cyclopentylene, and cyclohexylene.
The alkyl groups represented by R44, R45, R46, R49 and R50 preferably have 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms, and may be straight, branched or cyclic. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, hexyl, nonyl, decyl, dodecyl, tridecyl, cyclopentyl, and cyclohexyl.
Where R44 and R45, R45 and R46, R44 and R46, R44 with R45 and R46, and R49 and R50 form rings, the rings preferably have 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atomsxe2x80x2, and may have pendant alkyl groups of 1 to 6 carbon atoms, and especially 1 to 4 carbon atoms.
S, T, and U are each integers from 0 to 20, preferably from 1 to 10, and more preferably from 1 to 8.
Illustrative examples of the compounds of formulas (B)-100 and (B)-101 include tris{2-(methoxymethoxy)-ethyl)amine, tris(2-(methoxyethoxy)ethylamine, tris[2-((2-methoxyethoxy)methoxy}ethyl]amine, tris(2-(2-methoxyethoxy)-ethyl)amine, tris{2-(1-methoxyethoxy)ethyl)amine, tris{2-(1-ethoxyethoxy)ethyl)amine, tris(2-(1-ethoxypropoxy)-ethyl}amine, tris[2-((2-hydroxyethoxy)ethoxy)ethyl]amine, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, 4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane, 1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, and 1-aza-18-crown-6.
The resist composition of the invention may include, as an optional ingredient, a surfactant which is commonly used for improving the coating characteristics. Optional ingredients may be added in conventional amounts so long as this does not compromise the objects of the invention.
A nonionic surfactant is preferred, examples of which include perfluoroalkyl polyoxyethylene ethanols, fluorinated alkyl esters, perfluoroalkylamine oxides, and fluorinated organosiloxane compounds. Illustrative examples include Florade FC-430 and FC-431 from Sumitomo 3M Ltd., Surflon S-141, S-145, S-381 and S-383 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403, and DS-451 from Daikin Industries Ltd., Megaface F-8151, F-171, F-172, F-173 and F-177 from Dainippon Ink and Chemicals, Inc., and X-70-092 and X-70-093 from Shin-Etsu Chemical Co., Ltd. Preferred surfactants include Florade FC-430 from Sumitomo 3M Ltd. and X-70-093 from Shin-Etsu Chemical Co., Ltd. Also, nonionic surfactants of various hydrocarbon chains may be added for improving the wetting of resist with a developer.
Pattern formation using the resist composition of the invention may be carried out by a known lithographic technique. For example, the resist composition may be applied onto a substrate such as a silicon wafer by spin coating or the like to form a resist film having a thickness of 0.1 to 1.0 xcexcm, which is then pre-baked on a hot plate at 60 to 200xc2x0 C. for 10 seconds to 10 minutes, and preferably at 80 to 150xc2x0 C. for xc2xd to 5 minutes. A patterning mask having the desired pattern may then be placed over the resist film, and the film exposed through the mask to an electron beam or to high-energy radiation such as deep-UV rays having a wavelength below 300 nm, an excimer laser, or x-rays in a dose of about 1 to 200 mJ/cm2, and preferably about 10 to 100 mJ/cm2, then post-exposure baked (PEB) on a hot plate at 60 to 150xc2x0 C. for 10 seconds to 5 minutes, and preferably at 80 to 130xc2x0 C. for xc2xd to 3 minutes. Finally, development may be carried out using as the developer an aqueous alkali solution, such as 0.1 to 5%, and preferably 2 to 3%, tetramethylammonium hydroxide (TMAH), this being done by a conventional method such as dipping, puddling, or spraying for a period of 10 seconds to 3 minutes, and preferably 30 seconds to 2 minutes. These steps result In the formation of the desired pattern on the substrate. Of the various types of high-energy radiation that may be used, the resist composition of the invention is best suited to fine pattern formation with, in particular, deep-UV rays having a wavelength of 254 to 120 nm, an excimer laser, especially ArF excimer laser (193 nm), F2 excimer laser (157 nm), Kr2 excimer laser (146 nm), KrAr excimer laser (134 nm) or Ar2 excimer laser (126 nm), soft x-rays of 13 nm, 11 nm and 8 nm, x-rays, or an electron beam. The desired pattern may not be obtainable outside the upper and lower limits of the above range.
The resist composition comprising the amine compound according to the invention is effective for preventing a resist film from thinning and for expanding the focus margin while achieving an improved resolution.